I would imagine salt grains can burn. It's very important to mix the salt in water before adding it to the tank. Obviously the coral was not happy with this salt falling on top of it. When in a hurry like taht, either wait until you have time to top off the water or top it off and deal with adding salt later.
Keep an eye on the coral. If you suspect injury you can dip the coral in a special coral disinfectant made just for coral. Do not use RTN
dips. I forgot who makes it, but the bottle has a first aid red cross on it labelled coral disinfectant. Do exactly what's directed on the bottle. This disinfectant is great for wounds. It provides a slime coat that helps protect the wounded areas from infection while the flesh underneathe heals. Corals have amazing healing and regenerative capabilities.
We, as a people, know so much more about outer space than we do about our own oceans. This lack of knowledge can very well spell the dangers that lay in wait for us.
The oceans surely would swallow us before a rock comes down to smite the planet of it's life.